Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Reverse transcriptase from foamy virus, strain H4188 was estimated and purified. The enzyme has the following characteristics: 1. The reaction utilized preferentially oligo (dT) poly (rA) as a primer-template; however, the synthetic primer-template oligo (dT) poly (dA) could also be used to some extent. 2. The reaction utilized oligo (dG) poly (rC) as a primer-template with very low efficiency. 3. The crude virus preparation had a detectable endogenous reaction using the four deoxyribonucleotides for DNA polymerization. 4. The cation requirement for the enzyme reaction was much more biased for Mn++ than for Mg++ ions. 5. The molecular weight of the partially-purified enzyme was estimated to be about 80,000. Aggregates of 240,000 daltons were also seen. The activity of this enzyme was not inhibited by antisera against the reverse transcriptases of various type C RNA viruses, namely, feline endogenous leukemia virus, RD 114, Woolly simian sarcoma virus (SSV-1) and avian myeloblastosis virus (AMV). Antiserum against Rauscher leukemia virus (RLV) enzyme was marginally active against foamy virus enzyme, perhaps indicating a slight cross-reaction. The biochemical characteristics of foamy virus reverse transcriptase seemed to be very close to those of the type C RNA viruses, but the immunological reaction proved that the foamy virus reverse transcriptase was distinct from the others.
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PMID:Reverse transcriptase of foamy virus. Purification of the enzymes and immunological identification. 7 44

Reverse transcriptase (RT; RNA-dependent DNA nucleotidyltransferase) from Rauscher leukemia virus is synthesized in infected cells by way of a read-through poly- rotein of 200,000 molecular weight. This polyprotein (Pr200(gag-pol)) was precipitated by antiserum to RT; in a previous study all the monospecific antisera to gag proteins recognized Pr200(gag-pol). Pr200(gag-pol) contains both p30 and RT peptide sequences. Intermediate RT-related precursors of 145,000 (Pr145(pol)), 135,000 (Pr135(pol)), and 125,000 (Pr125(pol)) molecular weights were specifically recognized by precipitation from infected cell extracts by antiserum to RT. These proteins shared methionine-containing tryptic peptide sequences with a virion polypeptide of 80,000 molecular weight (p80(pol)) precipitate by antiserum to RT. Purification of active RT enzyme from virions labeled with [(3)H]methionine showed that p80(pol) was the major component, based on analysis by gel electrophoresis and tryptic peptide mapping experiments. A polypeptide (Pr80(pol)), similar in size to mature viral p80(pol), was also precipitated from infected cells by antiserum to RT. Its peptide map was nearly identical to that of virion p80(pol). Pulse-chase studies showed that Pr80(pol), Pr125(pol), and Pr135(pol) were stable polypeptides, whereas Pr200(gag-pol) and Pr145(pol) were unstable precursors. Pulse-chase studies with the protein synthesis inhibitor, cycloheximide, showed that the processing of Pr200(gag-pol) occurred for a short time in the absence of protein synthesis.
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PMID:Biosynthesis of reverse transcriptase from Rauscher murine leukemia virus by synthesis and cleavage of a gag-pol read-through viral precursor polyprotein. 7 22

beta-Lapachone is a naturally occuring compound that can be isolated from a number of tropical trees. It is shown to be a potent inhibitor of reverse transcriptase activity from both avian myeloblastosis virus and Rauscher murine leukaemia virus. In addition, it affects eukaryotic DNA-dependent DNA polymerase-alpha activity: 50% inhibition is reached in 60-min incubation time by about 8 micron beta-lapachone. Enzyme activity is inhibited irrespective of the purity of the enzyme used or of the amount or type of template/primer or substrate present. The inhibitory effect of the drug is only observed in the presence of dithiothreitol. The primary site of action of beta-lapachone appears to be the enzyme protein, as is also borne out by the specificity of its action. Eukaryotic DNA-dependent DNA polymerase-beta, prokaryotic DNA-dependent DNA polymerase I, several other nucleic acid polymerases and some completely unrelated enzymes are not affected. Reverse transcriptase and DNA-dependent DNA polymerase-alpha may be in someway related in possessing similarly exposed '--SH structures' in their active sites. beta-lapachone thus affords a novel means of studying such interrelationships and of further characterizing enzymes.
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PMID:beta-Lapachone, an inhibitor of oncornavirus reverse transcriptase and eukaryotic DNA polymerase-alpha. Inhibitory effect, thiol dependence and specificity. 7 23

Reverse transcriptase and p30 were purified from various retroviruses and the intra- and interspecific interaction between the two proteins were studied. The intraspecific complex stimulates [3H]TMP incorporation into (dT)12.(rA)n severalfold above that of the enzyme itself whereas DNA synthesis in the presence of the interspecific complex can stimulate DNA synthesis about 1.5-fold. The sedimentation rate value of the intraspecies complex varies between 12 and 16 S with an estimated molecular weight of 400,000. The molar ratio of p30:reverse transcriptase within the complex is 8:1. Both complexes can be dissociated into their original protein components by exposure to salt (kcl) solution, except that 0.3 M KCl will dissociate the interspecies complex whereas 0.8 M KCl is required for dissociation of the intraspecies complex. Competition studies in which an interspecies complex was exposed to p30 autologous to reverse transcriptase within the complex resulted in the displacement of the heterologous (p30) protein and the formation of a new intraspecific complex.
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PMID:Effect of RNA tumor virus-specific protein p30 on reverse transcriptase. Intraspecies and interspecies interaction between reverse transcriptase and p30. 8 36

Buffy coats from 31 patients with a diagnosis of leukemia and 16 normal donors were tested for the presence of a viral-like reverse transcriptase. Eighty-five percent of fresh leukemic buffy coats were positive. Also tested were spleens from 16 patients with hematological disorders and 5 spleens from patients without history of hematological malignancy. The 5 normal spleens were negative. Also negative were 4 spleens from patients with Hairy cell leukemia. From the remaining 12 spleens 7 were positive. Reverse transcriptase measurements can be used to distinguish leukemic from normal buffy coats.
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PMID:On the presence of reverse transcriptase in myelo- and lymphoproliferative disorders. 8 54

Samples of three nonmalignant and seven leukemic human cells were examined for DNA polymerase activity that could be identified as RNA tumor virus reverse transcriptase. Experiments on virus-infected model animal cells provided the basis for cell fractionation procedures, and reconstituted systems of known virus, added to human cells, established a threshold of virus detection by enzyme assay at 1 to 10 particles/cell. DNA polymerase activity with some properties similar to a reverse transcriptase was detected in some of the human leukemic cells. However, parallel analyses of nonmalignant cells showed sufficient similarities to raise serious questions about the specificity of the criteria. Reverse transcriptase activity has been reported to be present in white blood cells from a proportion of cases of leukemia; however, it is concluded from the present study that the usual enzymatic criteria using synthetic template primers, which were used in most of the studies reported, are not sufficient to identify a DNA polymerase activity as viral reverse transcriptase.
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PMID:Detection of reverse transcriptase activity in human cells. 8 60

A long-term cell culture of human glioblastoma was investigated microscopically, virologically, and biochemically. Reverse transcriptase activity was detected in cultured human glioblastoma cells. 3H uridine was incorporated into particles of buoyant density at 1.07 g/ml (Ficoll) which is equal to that of Oncorna virus particles, but 3H thymidine was not incorporated at all. Furthermore, reverse transcriptase activity was also demonstrated with the particles, suggesting that the cultured human glioblastoma cells were producing type C Oncorna virus. Ultrastructural observations of cell culture of glioblastoma showed type C virus particles in cisternae and culture medium. Budding of the virus was also seen on the surface of the cell. The mean diameter of the particles was approximately 100 nm. Ca. 1.1 nm of spikes protruded from the envelope. Both types of virions were observed, i.e. the doughnut-shaped type form and the solid circular form.
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PMID:Type C particles in culture of human glioblastoma cells. 8 68

A procedure using the virus-associated reverse transcriptase was developed for following the kinetics of adsorption, penetration, and uncoating of murine leukemia virus. Viral adsorption to cell membrane was determined by assaying this enzyme activity in isolated debris of mechanically disrupted cells after infection with murine leukemia virus in the presence of actinomycin D. At 37 degrees C, viral adsorption proceeded at a high initial rate, but after 5 min of incubation with the virus, it gradually slowed down. At 4 degrees C, viral adsorption was slower but proceeded at a linear rate. Intracellular virus was determined by centrifuging the cytoplasmic fraction of the disrupted cells at 105,000 x g for 45 min and assaying reverse-transcriptase activity in the high-speed pellet thus obtained. Sucrose gradient analysis of the enzyme activity recovered from the cytoplasm of infected cells indicated that this activity represented intact virus particles. No appreciable amount of such particles was recovered from the cytoplasm of cells infected at 4 degrees C. This indicates that the virions recovered from the cytoplasm of cells infected at 37 degrees C are indeed intracellular virus particles which penetrated into the cells and not just membrane-bound particles mechanically released to the cytoplasmic fraction during cell disruption. By this procedure intracellular virus was found to accumulate in the cytoplasm, reaching a maximal level within 20 min. The accumulated intracellular virus particles gradually disappeared from the cytoplasm, evidently due to their uncoating which was completed within 80 min.
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PMID:Adsorption, penetration, and uncoating of murine leukemia virus studied by using its reverse transcriptase. 9 Jan 59

UV irradiation of infectious vesicular stomatitis virus was employed to study the relationship between the expression of certain viral gene functions and viral inhibition of RNA synthesis in mouse myeloma (MPC-11) cells. Viral infectivity, protein synthesis, and viral mRNA synthesis were all highly susceptible to inactivation by UV radiation; however, low levels of viral transcriptase activity were detected in vitro in virus preparations subjected to large doses of UV radiation. In sharp contrast, the capacity of vesicular stomatitis virus to shut off cellular transcription was quite resistant to UV radiation. The data presented here indicate that viral transcription is essential to inhibit host RNA metabolism, even though synthesis of viral polypeptides in the inhibited cells could not be detected. At those levels of UV radiation that inactivated all viral gene functions, except viral inhibition of cellular RNA synthesis, the only viral product detected was non-adenylated, low-molecular-weight RNA species.
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PMID:Use of UV irradiation to identify the genetic information of vesicular stomatitis virus responsible for shutting off cellular RNA synthesis. 9 Jan 65

An RNA-dependent RNA polymerase has been completely purified from Cauliflower inflorescences. Analysis of the purified enzyme on SDS-polyacrylamide gels showed one polypeptide chain with a molecular weight of 140,000 dalton. The enzyme is monomeric in its native state. The in vitro activity was completely dependent on added RNA, the most efficient templates being poly (U), poly (U, C), poly (I) and viral RNA.
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PMID:[Purfication and molecular weight of an RNA-dependant RNA polymerase from Brassicae oleracea var. Botrytis]. 10 17


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